1. Technical Field of the Invention
The present invention relates to an electro-optical device and also to an electro-optical device provided in an electronic apparatus.
2. Related Art
In recent years, proposals have been made as to a structure in which a planarized interlayer insulating film is provided between a thin film transistor (TFT) and a lower electrode of an organic EL element in an organic active EL emissive device. The organic active EL emissive device comprises a plurality of TFT's and a plurality of organic EL elements driven by the TFT's and arranged corresponding to the TFT's.
FIG. 10 illustrates a known example of this type of organic active emissive device.
An organic active emissive device 148 comprises a thin film transistor (TFT) 150 on a substrate 149, an organic EL element 154 including a counter electrode 151, an organic layer 152 and a lower electrode 153, and an interlayer insulating film 155. In addition, the terminal of the TFT 150 is electrically connected to the lower electrode 153 of the organic EL element 154 through a contact hole 156 made in the interlayer insulating film 155 such that the TFT 150 drives the organic EL element 154.
The thin film transistor (TFT) 150 comprises a first transistor (Tr1) 157 and a second transistor (Tr2) 158 shown in FIG. 11. Moreover, electric current passes through scanning electrode lines (Yj to Yj+n) 159, signal electrode lines (Xi to Xi+n) 160 and common electrode lines (Ci to Ci+n) 161 such that the organic layers 152 of the organic EL elements 154 are driven.
Also, capacitors 162 are formed between the common electrode lines (Ci to Ci+n) 161 and the first transistors (Tr1) 157, respectively, so as to store electric charges.
The interlayer insulating film 155 is provided over the thin film transistor (TFT) 150 and planarized at the surface contacted with the lower electrode 153.
In addition, an electro-optical device of active-matrix structure shown in FIG. 12 has been proposed as another type of conventional device.
In FIG. 12, an electro-optical device 170 of a conventional active-matrix structure comprises: a glass substrate 171; a first polysilicon layer 172 as an active layer formed on the surface of the glass substrate 171; a gate insulating film 173 formed by thermally oxidizing the poly-silicon layer 172; a second poly-silicon layer 174 as a gate electrode; a first interlayer insulating film 175; a second interlayer insulating film 176; a signal electrode line 178; a first contact hole 179; a second contact hole 180; a first pixel electrode 181; a second pixel electrode 182; and an insulating film 183.
In the electro-optical device 170 of the active-matrix structure, the insulating film 183 is formed and planarized after laminating the first poly-silicon layer 172, the gate insulating film 173, the second poly-silicon layer 174, the first interlayer insulating film 175, the second interlayer insulating film 176 and the signal electrode line 178.
In the above conventional organic active emissive device 148, needs to improve the property that insulates the lower electrode 153 from the scanning electrode line 159, the signal electrode line 160 and the thin film transistor 150 provided below the interlayer insulating film 155 in order to prevent faulty luminance of the organic EL element 154 and defects in the process of forming electrodes. Hence, it has been required to form the interlayer insulating film 155 that exhibits such sufficient insulating property.
However, it is not easy to planarize the interlayer insulating film 155 with high precision, and there has been such a problem that faulty luminance of the organic EL element and/or the defects in the process of manufacturing electrodes occur when a sufficient insulating property is not obtained.
Moreover, in the case of the above electro-optical device 170 of the active-matrix structure of another type of prior art, the insulating film 183 is formed and planarized after depositing the first pixel electrode 181; however, there has been such a problem that it is difficult to planarize the insulating film 183 to be formed over the first pixel electrode 181 because the second interlayer insulating film 176 and the first pixel electrode 181 have irregularities.
The present invention has been made in light of the above circumstances. One goal of the invention is to provide an electro-optical device having a large aperture ratio, and with which it is possible to easily planarize insulating films laminated over a switching element, a wiring and an insulating film constituting the electro-optical device.